When a subject is shot by a video camera, holding of the video camera directly by a person with their hands or mounting of the video camera on a moving body, such as a vehicle, causes fluctuation at the time of shooting to appear on the screen. Therefore, a hand-vibration correction apparatus has been put into practical use, in which an image fluctuation is detected from a video signal and position corrections of the image are made on the basis of this fluctuation information. Such a hand-vibration correction apparatus needs an image fluctuation detection apparatus for detecting the fluctuation of the image.
As a representative example thereof, a method of detecting an image fluctuation from an image signal after shooting, performing image position corrections on the basis of the fluctuation information, and thereby removing the fluctuation will first be described (Technical Report, The Institute of Television Engineers of Japan, vol. 11, no. 3, May 1987).
An image signal having an image fluctuation first undergoes A/D conversion and is distributed to two systems. The signal supplied to one of the two systems is transferred to a Y/C separation circuit. Only a Y signal is taken out therein and transferred to a motion vector detection circuit. In the motion vector detection circuit, an operation resulting in generation of an optimum correction vector is performed while undergoing control concerning the detection area.
On the other hand, the signal supplied from the A/D conversion circuit to the other of the two systems is transferred to a delay circuit and delayed therein by a time requires for the motion vector detection circuit to detect the motion vector and generate a correction vector. Thereafter, it is written into a memory and then undergoes processing such as control over the read address, image expansion and interpolation. The signal thus processed is transferred to a D/A conversion circuit to become an output signal.
A method of detecting an image fluctuation from an image signal during shooting, performing image position corrections on the basis of the fluctuation information, and thereby removing the fluctuation will now be described (IEEE Transactions on Consumer Electronics, vol. 36, no. 3, August 1990).
An video signal having an image fluctuation first undergoes A/D conversion and is distributed to two systems. The signal supplied to one of the two systems is transferred to a motion vector detection circuit. Only a required signal component is taken out by a filter circuit and an optimum correction vector is generated.
On the other hand, the signal supplied from the A/D conversion circuit to the other of the two systems is written into a memory and then undergoes processing such as control over the read address, image expansion and interpolation according to the correction vector. The signal thus processed is transferred to a D/A conversion circuit to become an output signal.
In the above described configuration, however, consideration is not given to discrepancy of a half line in vertical direction caused by interlace between fields of a video signal. Therefore, the above described configuration has a problem that this error of a half line in vertical direction is included in the correction vector for correcting the image fluctuation.
The present invention aims to solve such a problem of the prior art. A technical subject of the present invention is to improve the precision of image fluctuation detection in vertical direction.